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Stones in your coffee?

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  • Stones in your coffee?

    I recently had a stone go through my grinder using beans from a local roaster. His response wasn't very sympathetic, along the lines of "things sometimes get through", and meanwhile my grinder now has a rattle which it didn't before.

    I changed suppliers after this, and recently I was surprised to find another stone in a bag from this supplier. A similar response was received from this supplier.

    It's been about 18 months so far on my coffee journey, and until recently I had not experienced a single stone in any coffee I'd purchased. Needless to say, I'm watchful now.

    I'm just wondering if it's normal to periodically find foreign objects in a bag of beans? I know that there are tools called "de-stoners" which I'm sure many coffee roasters use, but I was just wondering how often stones and other material make it through? If I found a stone in my bag of Cornflakes, I'm pretty sure the manufacturer would be more sympathetic than what I've experienced from the coffee world.

  • #2
    Hello darren,

    It's always possible. A destoner will separate out items of greater mass than a typical coffee bean- so rocks stones, screws etc will be separated. Smaller items of similar mass to a been (often mud which looks like stones) can find their way into bags. The good thing is that these rarely cause problems with cafe quality grinders.

    What grinder do you have? Perhaps it might be a good idea to disassemble it and give it a clean.


    • #3
      The topic is pretty taboo among roasters... most won't commment for fear of being liable for damage done.

      For whatever reason, only a fraction (a fairly small fraction at that) of roasters run a destoner.
      Have a look around their roastery and see if you can see something that looks like this: Coffee Destoner

      Most roasters that don't run one justify it with things like "I only buy good grade beans" but anyone who has run a destoner knows that you find all sorts of objects in all sorts of grades of green coffee.

      I've seen (from others) bullets, coins and even teeth! I've run a destoner for about 5 years and in that time might have found a kilo of small rocks, nails, nuts and bolts. Some of the "rocks" as Chris said will be lumps of mud or concrete and while not ideal will go through most grinders ok. Some of the rocks are much harder and will at best blunt your grinder, at worst damage the shaft on a domestic grinder.

      Cornflakes? I'm pretty sure the company will find plenty of rocks during their process too. Most would be pulled when they wash the corn, the rest would not get through the rollers I expect so it might be unlikely that you could get a rock in it.

      Coffee destoning should remove most rocks and hard objects if its tuned and adjusted ok for that batch of beans.

      At the snobbery we use a large mesh cooling tray that lets the smallest of the rocks fall through after roasting. I then destone the output and find the bigger ones and other dense objects. Anything with a density lower than a roasted coffee bean can still get through (eg small twig) but it would be sterile (roasted over 200C) and the grinder would munch through it ok.

      On rare occasions even with good process something gets through but at least I know I did my best to avoid it.


      • #4
        Breville Smart Grinder. The burrs seem to have suffered little, but as Andy replied, the shaft now seems bent slightly, which I think is causing the rattle. I added an extra shim which seems to have helped with this.

        Cornflakes was just an example. My point is that foreign items in other food products seem to be taken quite seriously by their manufacturers, most likely as they want to avoid bad press and/or litigation. That's why I was surprised to be given the "it happens" response from two different roasters. I would have thought at least they'd offer a free bag or beans or something as a sign of good faith.


        • #5
          Sure, I understood that cornflakes was just an example, I was also using it as an example of the manufacturing differences that actually help get rid of stones in cornflakes. It might be easier to find a bit of plastic in cornflakes, harder in coffee as it would have melted in the roaster (ewww).

          I would have thought at least they'd offer a free bag or beans or something as a sign of good faith.
          ...and that act would admit liability. Welcome to 2012+
          (sadly for common sense)


          • #6
            There is no excuse for anyone in *commercial* roasting to NOT run a destoner. Anyone that is selling coffee is a commercial roaster whether they are using a 1 kilo machine or a 300 kilo machine.

            That doesnt mean as others have said, that you wont get an occasional thing get through (where a "thing" could be anything not just a "stone") but in the main, most "things" that get through, proba bly didnt get through and instead fell into the coffee after destoning, when the coffee was being handled ie weighed, packaged etc. These items are then not "stones" but other items. Good destoners are adjustable, and when working properly will seldom allow items to get through even when judged over a great many tons of through put.

            If I knew that a certain roaster wasnt using a destoner, I wouldnt buy their product, and as far as I am concerned, its an unprofessional practice for a commercial roaster to NOT use a destoner (just as it is for them to NOT use air pollution gear).

            That's just my own personal opinion, and I hope that helps.


            • #7
              Gettin' stoned on coffee - what will they think of next.


              • #8
                Originally posted by Rocky View Post
                Gettin' stoned on coffee - what will they think of next.
                Perhaps some Brown Sugar. Oh wait, I see - not those Stones


                • #9
                  So foreign objects are fairly uncommon then? Sounds like it may have been a coincidence perhaps to experience this twice with two different roasters.


                  • #10
                    Originally posted by flynnaus View Post
                    Perhaps some Brown Sugar. Oh wait, I see - not those Stones
                    Of course not! It's the Stone Roses......'She Bangs the Drum (Roaster)'


                    • #11
                      Originally posted by Barry O'Speedwagon View Post
                      Of course not! It's the Stone Roses......'She Bangs the Drum (Roaster)'
                      Ah, of course <slaps forehead> but I thought you might have opted for your namesake's "Can't Stop Rockin (My Roasts)"


                      • #12
                        But I missed the obvious Stone Roses classic '(Are You) Made of Stone'. I guess we'd better stop or start an 'Off Topic' thread.


                        • #13
                          I found a stone in some raisin bread once, rang up the manufacturer, got the bread free


                          • #14
                            Who paid for the dental work?


                            • #15
                              Carly Simon had 'clouds in her coffee' - do you think she should get a refund on the beans?